Advanced Cell Technology (ACT) has released the first positive, peer-reviewed [pdf] report about a treatment derived from human embryonic stem cells. The news was called a "miracle" and a "ray of light" by a few, normally sober, newspapers. And, by an amazing coincidence, ACT simultaneously started their previously announced, closely related, UK trial. The company's stock gained 23% (albeit only to 18¢), which would be more impressive had it not lost 61% last year.

The Los Angeles Times and Washington Post had more tempered responses. And the New York Times noted that ACT "has been criticized in the past for overstating results, in part because it has been desperate to raise money to stay in business." Moreover, "it is hard to judge much from only two patients, especially when there was no control group."

Both patients are happy — one says she can now thread a needle, and the other can navigate a mall. These improvements are modest, and it's possible that only one is significant, that of the patient who improved from virtually complete lack of sight to 20/800 vision in her treated eye. (She may still be legally blind; the definition is 20/200 or worse, even with corrective lenses.) The other patient improved from 20/500 to 20/320, but may be demonstrating a placebo effect, since her untreated eye also improved.

This could be a pointer to the start of a potentially promising therapy, but it's a shame to have it over-hyped. Will ACT end up crying wolf once too often?